1. Field of the Invention
The present invention relates to an apparatus for controlling the driving of an electric motor for opening and closing the door of an elevator.
2. Description of the Related Art
FIG. 3 shows the mechanical structure of a door apparatus for elevators.
In FIG. 3, reference numeral 1 denotes an elevator door, reference numeral 2 denotes an entrance of a cage, reference numeral 3 denotes a door hanger fixed at the upper end of the door 1, reference numeral 4 denotes a hanger case for holding the door hanger 3, and reference numeral 5 denotes a rail provided on the hanger case 4. Reference numerals 6 and 7 denote hanger rollers and upward thrust rollers, respectively, which are moved on the rail 5 so as to guide the door 1 to be opened and closed. Reference numeral 8 denotes an attachment apparatus which is provided on the door 1 and which is engaged with an apparatus (not shown) provided on an unillustrated door of an elevator shaft prescribed within a elevator shaft zone of the elevator shaft so as to cause the door 1 to interlock with the elevator shaft door in the prescribed zone. Reference numeral 9 denotes a drive apparatus which is provided on the hanger case 4 for the purpose of driving the door 1, reference numeral 10 denotes a door driving motor contained in the driving apparatus 9, and reference numeral 11 denotes a four-throw driving link for opening and closing the door driven by the driving apparatus 9. Reference numeral 12 denotes a CLT sensor which indicates a closed state of the door, reference numeral 13 denotes a safety gate switch which also indicates a closed state of the door, and reference numeral 14 denotes an OLT sensor which indicates an open state of the door 1. Reference numeral 14A denotes a dog for actuating the sensors, and reference numeral 14B denotes an inverter apparatus for driving the door motor.
As shown in FIG. 4, when the OLT sensor 14 is turned on in an open state of the door 1, the sensor 14 outputs an OLT signal having a level "1". When the CLT sensor 12 is turned on in a closed state of the door 1, the sensor 12 outputs a CLT signal having a level "1". When the gate switch 13 is turned on during the course of transition from an open state to a closed state of the door, the switch 13 outputs a gate switch signal S.sub.G having a level "1".
FIG. 5 shows an example of a vector control inverter circuit for driving the above-described door system for an elevator. For example, a three-phase alternating current or a single-phase alternating current of 200 V or 220 V, which is input from a power source, is rectified by a diode bridge 15 and smoothed by a smoothing capacitor 16 to generate a dc voltage. The dc voltage is converted to a sine-wave motor current by an inverter 17 comprising switching elements such as transistors, FET's or the like. During this control, the switching elements of the inverter 17 are subjected to pulse width modulation by the PWM pulse generated from a PWM pulse generator 19. In this way, the speed and torque of the door driving motor 10 are controlled.
The speed of the door driving motor 10 is detected by an encoder 10A provided on the motor shaft. The speed .omega..sub.r.sup.* detected by the encoder 10A is added to the speed command .omega..sub.r generated from a speed command generator 22 at a first addition point 23 to determine a speed deviation .DELTA..omega..sub.r. When the speed deviation .DELTA..omega..sub.r is input to a speed amplifier 24, the amplifier 24 calculates the torque necessary for the door driving motor 10 in accordance with the speed command .omega..sub.r and inputs to a slip calculating section 26 a torque command, e.g., a current iq corresponding to the torque and a current command id corresponding to excitation, which is generally a constant value within a constant torque region. The slip calculating section 26 generates a slip frequency .omega..sub.s. The slip frequency .omega..sub.s is added to the speed .omega..sub.r.sup.* detected by the encoder 10A at a second addition point 27 and then input to a phase counter 28 serving as an integrator. In the phase counter 28, the rotational angle of the driving motor is calculated by the equation .theta..sub.r =.intg.(.omega..sub.r.sup.* .+-..omega..sub.2) dt.
The phase angle ##EQU1## which is calculated from the current iq corresponding to the torque and the current command id corresponding to excitation by a phase angle calculating section 30, is added to the rotational angle .theta..sub.r of the magnetic field at a third addition point 29 to determine an actual current phase angle .theta.=.theta..sub.r +.theta.i. From the phase angle .theta. and the current amplitude I generated from a current amplitude calculating section 25, a current command generating section 21 generates a U-phase current command Iu=.vertline.I.vertline..multidot.sin .theta. and a V-phase current command I.sub.v =.vertline.I.vertline..multidot.sin (.theta.+2/3 .pi.). From the current commands and the actual motor currents I.sub.u.sup.*, I.sub.v.sup.*, which are respectively detected by dc current transformers 18, deviations .DELTA.I.sub.u, .DELTA.I.sub.v and .DELTA.I.sub.w =-I.sub.u -.DELTA.I.sub.v are determined by a DC amplifier 20. A three-phase PWM voltage command corresponding the three deviation values is generated from a PWM pulse generator 19. The pulse train is supplied to the inverter 17 so as to actuate the switching elements thereof. This permits the current, voltage and frequency of the door driving motor 10 to be controlled to predetermined values. The above-described series of operations controls the rotational speed and the torque of the door driving motor 10.
In the vector control inverter, a section 31 shown by a one-dot chain line in FIG. 5 comprises a microcomputer. FIG. 6 shows an example of the configuration of the microcomputer. In the drawing, reference numeral 45 denotes a CPU for executing the command read by a read only memory ROM 46. Reference numeral 51A denotes a RAM for storing data. Reference numeral 50 denotes an I/O interface for storing ir the CPU the CLT signal, OLT signal, open-door command signal S.sub.o, close-door command signal S.sub.c, gate switch signal S.sub.G and an active signal S.sub.u, all of which are input from external sensors. Reference numeral 48 denotes a timer for generating the slip frequency .omega..sub.s. The period of the slip frequency .omega..sub.s is supplied to the timer 48 from the CPU 45. Reference numeral 47 denotes an I/O interface for outputting the polarity of the slip frequency .omega..sub.s, i.e., slip sign output .omega..sub.s .+-.. Reference numeral 49 denotes a reversible counter for counting the speed detection pulse trains generated by the encoder 10A provided on the motor shaft.
FIG. 7 shows an example of a circuit for generating the U-phase current command I.sub.u and the V-phase current command I.sub.v by using the slip frequency .omega..sub.s, the current amplitude command .vertline.I.vertline. and the phase angle command .theta.i, all of which are output from the microcomputer 31 configured as described above. In the drawing, reference numeral 32 denotes a circuit for discriminating between the directions of the pulses PHA and PHB, which are encoder feedback pulse trains having phases 90.degree. shifted from each other, to output the pulses as a normal pulse CWP and a reverse pulse CCWP.
FIG. 8 illustrates the pulses PHA and PHB input to discriminating circuit 32 and the pulses CWP and CCWP by the discriminating circuit 32.
In FIG. 7, reference numeral 33 denotes a circuit for calculating the rotational angle .omega..sub.r =.intg.(.omega..sub.r.sup.* .+-..omega..sub.s) dt in combination with a phase counter 34. The slip pulse trains .omega..sub.s are divided into the signs + and -, which are input to the phase counter 34, on the basis of the slip sign output .omega..sub.s .+-. from the microcomputer 31. The relation between the rotational direction of the motor 10 and the slip sign output .omega..sub.s 35 is the following:
Normal rotation: input+during power running and input-during regeneration PA1 Reverse rotation: input-during power running and input+during regeneration
The encoder feedback pulse trains CWP, CCWP and the slip pulse train .omega..sub.s are input to the phase counter 34 with a phase shift by using a synchronous circuit (not shown), as shown in FIG. 9, so that the rotational angle .theta..sub.r =.intg. (.omega..sub.r.sup.* +.omega..sub.s) dt can be calculated. In the drawing, reference numerals 41 and 41A denote AND gates; reference numeral 42 denotes an inverter gate, and reference numerals 43 and 44 denotes OR gates. The values sin .theta.=sin (.theta..sub.r +.theta..sub.i) and sin (.theta.+2/3 .pi.)=sin (.theta..sub.r +.theta..sub.i +2/3 .pi.) are output from ROM 35, which serves as a sine wave table, on the basis of the output .theta..sub.r from the phase counter 34 and the phase output .theta..sub.i from the microcomputer 31. On the basis of the above digital output and the current amplitude output .vertline.I.vertline. from the microcomputer 31, the multiplication type D/A converters 37, 38, 39 of a current command generating circuit 40 generate the following analog values of current command output: EQU I.sub.u =.vertline.I.vertline..multidot.sin (.theta..sub.r +.theta..sub.i).times.Vref EQU I.sub.v =.vertline.I.vertline..multidot.sin (.theta..sub.r +.theta..sub.i +.intg. .pi.).times.Vref.
During the control of the door of an elevator driven by the vector control inverter which operates on the basis of the above-described principle, an abnormality detecting circuit 52A is generally added to the circuit shown in FIG. 7, as shown in FIG. 10, for the purpose of detecting the abrupt opening of the door, which is caused by a malfunction of the microcomputer 31 during the operation of the elevator. The abnormality detecting circuit 52A comprises a flip flop 51, NAND gates 54, 57, and an AND gate 55, and an inverter gate 56. If the gate switch 13 shown in FIG. 3 is turned off and outputs a gate switch signal S.sub.G level of "0" during the movement of the elevator, the output from the NAND gate 57 has a level of "0" because the active signal S.sub.u has a level of "1". A signal having a level of "0" is input to the set terminal of the flip flop 51 through the AND gate 55 so as to set the flip flop 51 to output a gate cutoff signal to the inverter 17. This operation causes the driving of the motor 10 to be stopped.
In the same way as described above, if the elevator lifting control board of the elevator inputs the active signal S.sub.u having a level of "1" to the circuit 52A in a state when the door is closed, and the encoder 10A inputs the reverse pulse CCWP, i.e., the open-door pulse, to the circuit 52A, the circuit 52A detects an abnormality. As a result, the output from the NAND gate 54 takes on a level of "0", and the flip flop 51 is set so that the gate cutoff signal is output to the inverter 17.
In this method, however, even if the motor 10 is driven by an appropriate driving control signal or driving output in the direction causing the door to close, when the motor 10 is rotated in the opposite direction by forcing the door to open, or when the door is slightly pushed back and vibrates at the door stop position when being closed, the encoder 10A engaged with the motor 10 outputs the pulse CCWP with a reverse phase. This output sets the flip flop 51 and cuts off the gate of the inverter 17 so that the motor 10 is stopped. Since there is thus no pushing torque in the direction of closing of the door, the door can be easily opened manually. This method thus has the problem that the passengers of the elevator are brought into a very dangerous condition.